You need to worry about this as police has jailed your relatives. Now, only solution you have is to get the bail for them who are in jail. Contact some criminal lawyer of your area and he will do the rest. It is very obvious case and they will get bail easily.
If any girl is above 18 years then there can not be case of abduction if she has gone willingly with the boy. But, on return when such girls go to their parents then they change their mind as per wishes of her parents. In such circumstances, you need to think of some strategy and to have this in advance take the help of lawyer and he will guide you.