Is my Lucy a Lucas? She seems rather friendly towards Sheldon. She is always on his back. ( ps not sure if they are male or female as they still 2 to 3 years old I think. Only had them for 6 months. Previous owner told me they were 2 years old)
Without a photo of the plastron (undershell) including the tail and the length of your tort, we can't tell.
Both Males and females will mount, butt and bite when they decide they don't want to share their accommodation any more. So the message you really need is that it is probably time to give each their own enclosure.
Need pic of underside tail area. Either way, they need to be separated. If he is a male and she a female and she is the on,y female, he will pester her to illness or death, unless they are in a very large yard with lots of sight barriers and separate hides, etc.