It's probably not a good idea from a tax point of view.
Your sons will have to pay stamp duty on the transaction.
If one of them subsequently wants to sell his share in the house to the other two, more stamp duty.
If the house rises in value between now and when they sell it, there will be CGT.
Your son who lives in the house will be exempt from Capital Gains Tax and Gift Tax, but the other two won't be.
All three will lose their first time buyers exemptions, I think.
In general, it's better to leave assets in your will rather than give them while you are alive. There is no CGT and no stamp duty.
My own view, is that property should be left to one person rather than to be split between three people. You can leave it to Son A on condition that he gives cash for two thirds of its value to B & C.