Violation of RA 7610 Arcticle VI (a)

Any legal advice on the case of my brother. He was involved in a relationship with a twin sister (minors 13yrs old). Base on the complaint of the twins, my brother just approach them and started kissing them on separate occasions. But base on the statement of my brother and other witnesses, the twins were the one texting him to meet them and have not resisted during the act. My brother was drunk when he meet them that's why he was able to that (kissing only). Now their father knowing what had happened filed a case stating that my brother violated RA 7610 article vi (a) but the statement stated in the affidavit of the complainant is wrong. It came out that my brother just approach them and that they haven't text him to meet him. My brother was not able to file a counter affidavit yet. Any legal advice regarding this? Can he still file a counter affidavit? And in case he will be found guilty, what would be the corresponding penalty for such offense? Hope you can advise me. thanks!