Confused

[Sweetashell]

<FONT color=#ff0000>in the summer my boyfriend used to love hanging out over his friend's house and he had a younger sister that liked my boyfriend at first i didnt think much of it until she told me that her and my boyfriend did stuff and he grabbed her butt and all type of stuff and he never once told me until school almost started again but he denied it saying she asked him to sleep with her and he said what about her and she was like forget me but he denied ever doing anything else with her should i believe him since it took so long for him to tell me that</FONT>