my brother is 24 and he is dating a 16 year old and i know they have had sex. and her mom wants to press charges on him for it.and her mom is stating that my brother beats her, which is not true

can she press charges against him? and they also took him into custody for other reasons

what type of charges and how long do you think they would give him if he would to get convicted.?

Yes, the mother (or anyone with knowledge of a crime) can report it to police. It is a violation of state law for a 24 year old to have sexual intercourse with a 16 year old. A parent can file a complaint with the police and it is up to the prosecuting attorney to determine the charges, if any, that will be filed.

There is no way to determine what type of sentence he may recieve especially if there are other violations pending. If he is charged with "Unlawful Sexual Intercourse" under 261.5, he can be charged with a felony or a misdemeanor due to the age difference between them. He can also face civil penalties if convicted in criminal court.