Ok so this ones weird. Somehow a guy ends up on a deserted island except for one guy who was already living in the island. The island guy falls in love with the new guy and tricks him into eating a fruit and drinking something both of which will allow him to give birth. Then they gave smutty sex and yeah...that's all I remember. Any ideas?

This should probably be in the Yaoi/Yuri section, but there's a oneshot in Yokubou Shounen called Love Snatcher which might be what you're looking for.

It is thank you! 😀