Stardew Valley's Sebastian is the dark, brooding romance option who actually turns out to be a nerdy guy. He's Robin's son from her first marriage and step-son of her husband Demetrius. He can be tough to woo since he usually isn't found outside of his room during the day and has some peculiar likes that may be tricky to get a hold of, especially early on. With some knowledge and know-how, it's possible to win over this moody guy.
Source：https://www.cbr.com/stardew-valley-how-to-get-every-sebastian-heart-event/
