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☆˗ˏ✎ A lil ramble about Sylvester and his love life -
Sylvester is a flirty person - its how he tries to express interest with people, otherwise he'd just be playful with them. Other than that, he didn't really get the "player" mindset until he'd met and became bound to Erwin - to which Sylvester ended up being told that he wasn't allowed to date etc.
As a teen, he had a crush on two people, to which I'll only mention one since Valeria isn't my oc, but Eris is (I'm scared to get details wrong-). He ended up dating Eris, and was still the sweet, gentle mindset with the hint of flirty. He didn't even do anything seggsy with her until they were twenty four - (for multiple reasons; the Nobles wouldn't appreciate the Prince doing that before marriage and because he didn't see the need to, they were in love and that's all that mattered, really).
Sylvester literally only becomes a "fuck boy" after Erwin tells him he can't pursue a relationship - when all Sylvester wants is to get married, have a family and go back to Vorn so he can rule :sob:
TLDR: Sylvester doesn't like being a player, he wants an adorable nerd gf that he can sit and listen to ramble about things that he'll probably never understand - so he can fluster them and smother them in attention.