Sole propretorship can not be sold or passed on under the law but the other way of doing this would be convert the sole propretorship into a llp which is allowed and get one of the son onboard and later there dad can show that he sold his share to his other son and now dad can get out of the firm i.e. basically he passed his company to his son and it wont die with him.

In a sole proprietorship, the owner of the business and the business are a single entity. Only one person owns the company and instead of paying corporate taxes, the owner pays personal income tax on any profit.
The process to change a business structure (for example, change from a sole proprietorship to a corporation or partnership) is the same as starting a new business!.there are some steps:
- Create your new business structure in your state.
- Submit a new Business License Application to apply for a new Business License.
this will be the only way to add the 2 sons as partnership, because Sole Proprietorship is one owner company, and Sole Proprietorship dies only when the owner dies.

A sole proprietor owns the entire business assets as personal property, as mentioned above. With that being said, it is possible to transfer the company to another person. The sole proprietor is allowed to transfer the business by selling its tangible and intangible assets, essentially transferring the responsibilities to the new owner. Keep in mind, the owner would need to notify the buyer what he/she is buying. The value of the business can be determined through negotiations based on the replacement costs of tangible assets. Thus, a written agreement is formed to specify what parts of the business is being sold and the obligations in the name of the previous owner. The agreement should include both tangible and intangible assets.

A sole proprietorship is a business with one owner-employee who holds assets and is directly responsible for all business obligations. He also has sole control over the business. The phrase “passed on” suggests that the owner is transferring his business to another. How you transfer a sole proprietorship will depend on his personal preferences and tax concerns. He can transform the business into another type of organization, transfer the business through his will or assign the business assets to a trust.

According to LegalZoom, if the sons must create a new business since a sole proprietorship is non-transferable. Once the original sole proprietor dies and the business is transferred, all of the business’s assets must still pass through probate. The sons might have to settle the outstanding debts to protect the business’s assets from creditor claims. Settling debts and restarting the business may require significant amounts of money. Ultimately, the sons need to create a new business then transfer all of the former proprietorship’s assets into that organization.

http://info.legalzoom.com/sole-proprietorship-someone-dies-23863.html

As stated above, the sons would have to start a new business. In my opinion, this would be a good thing. The sons could start a partnership. The sons would probably not have to pay business income tax under a partnership and it would open the door to discuss just how the business is going to be run in dept. They would have to determine how the income, work and contributions are broken up and this could be a good way to go into a company on a good foot. It might also create conflict but if two sons are going into a business together, they have to be able to communicate enough to be able to determine how they want the business to be run.
http://info.legalzoom.com/can-sole-proprietorships-multiple-owners-23282.html

Unfortunately, in a sole proprietorship, the company cannot be passed down. It would simply have to be the same company name but a different company. The sons of the owner would not have any rights to the original company created. The owner can hire his sons but once he dies he cannot pass down the money earned. As stated by gingeranderson, the sons could go on to create a partnership.

With sole proprietorship, the owner has full responsibility as to how the company runs, and what is and is not allowed. The owner is allowed to make changes as they feel to help their business grow. However, of course, there is the impending future to think about. Unfortunately, when the owner of the company dies, the company dies with it. However, the owner does have the capability to pass down their equipment to their kids, or whomever they seem fit for the task. This does not mean that the company will be the same as it was when it was originally built. The two kids can take the equipment left behind and continue the business like the owner did, but essentially it becomes a different company. The sons can create a partnership to create this company, but that does not mean it is the same. In a sole proprietorship, the original owner will always be the holder of the company, and the future generations would have to create a new company.

Sole proprietorship cannot be passed on or transferred from dad to his sons. Unfortunately if dad dies, then the assests/company cannot be taken by his childern. His sons has no rights on the company their dad created. So in case of sole proprietorship, the company held by a person is solely his/hers. It cannot be transferred to their future generations. Its better sons start new business with partnership.

My father owns a company in which he has a sole proprietorship. A sole proprietorship is an unincorporated entity that does not exist apart from its sole owner. Unfortunately, my brother and I are not able to just be handed the company. If my dad wanted us to start running the company we would have to buy him out or he would have to pass away. Then my brother and I could split the company or sell it if we pleased.

As can be predicted by its name, a sole proprietorship has one owner who is fully responsible for the operation of the company. The owner makes decision that will affect the overall growth of the business. Its not possible for the owner to pass it on to his two sons because a sole proprietorship can only have one owner. However, the first step could be to convert the sole proprietorship into an LLP for the father to hand down to one of his sons.

father can execute sale deed for transfer of assets and liabilities of sole proprietary concern by father in name of 2 sons. There are other ways such as simthshah said is by converting it into LLP. Another way is by executing the gift deed and transfer all the capital to his two sons as a gift but the only catch is, the gift deeds are very hard to be transferred.

Source: https://www.kaanoon.com/83333/transfer-of-proprietorship-partnership-from-father-to-sons

As the name indicates, Sole proprietarship means the company has single owner. So the sons/children cannot cannot handle their dad company. Father has to sell the company. If the dad dies then his company cannot be transferred to his sons. Hence it is better that the sons start new business by doing partnership.

Sole proprietorship cannot shift its owner according to the law, the business will die with the owner. One way to do this is change the category to a Limited Liability Partnership which allows limited members to hold the company's share. In this case, the father must sell all the shares he owns to his sons, who are also the partners, before he dies, otherwise the company will still die with him. The other risks of running business as LLP are, professional skills demanded, recognition by State's law, and binding partnership.