Marrying my first cousing once removed

Respected P.Venu sir, all forms of marriage has been carried out in our custom.. including marriage between cousins, between uncle and niece, and i do have legal proofs for those registered marriages. So i wish to know if a marriage can be made legal between me (uncle) and her (first cousin once removed/niece) 

Yes, such marriage would be legal. Moreover, even under the provisions of Hindu Marraiage Act, the marriage within prohibited relations is void, not illegal, at the instance of the parties to the marriage and not otherwise.

@P.Venu Sir,  Thank you very much for the clarification sir.