For Silver's birthday, Malleus waits for the stroke of midnight to wish him happy birthday. If Silver won't wake up, then he'll just give him lots of happy birthday kisses in his sleep <3 He tries to make the day as enjoyable as possible, giving him tons of luxurious gifts and taking him on a gorgeous, fast-paced flight across the island. Silver would honestly prefer something more low-key, and has no idea what to do with these expensive, antique books ("I guess I can use them for weight training...?"), but he still thanks him, saying he doesn't deserve all these things <3 Malleus also takes care of the catering, no Lilias allowed in the kitchen!! In general though, I think Malleus would be sort of melancholic on his birthday. It's the day to celebrate his little beloved, but it also means one less year with him </3
For Malleus... Eheh. Silver will ask Lilia beforehand what he should get Malleus, and you know Lilia is already dragging out the fancy lingerie and bondage (Lilia, why do these fit Silver, and why do you have them....) He'll prepare himself just for Malleus <3 Dragon boy is going to town all morning long, Silver's ass is STUFFED by the time they're done. They take a bath together, and it's so soft and peaceful <3 (until Silver mentions that he also got Malleus a gargoyle for his birthday, getting Malleus in a fit because it was NOT a gargoyle...)