Seems like most of you will say own up and take responsiblity for it. Before owning up and becoming responsible for it, it's probably fair for the TS to confront the girl and:-

1) Inform of his stand
i.e (want/don't want) the baby, (want/don't want) marry the girl

2) Ask the girl what is her stand
i.e (want/don't want) the baby

3) If the answer is to not want the baby, then it comes to a moral decision. Abortion or adoption? If the girl wants the baby, and TS don't want, TS should conduct DNA test. For all you know it's not even his...

4) TS would need to decide whether he wants to give child support if the kid is his.

Regardless, I wouldn't comment or judge on who's right and who's wrong. It's their life and it's a mutual decision for them to fornicate. Both are equally at fault for the result.