Birthday present for DSS

[Notsurewhyimdoingthis]

It's my DSS's birthday next week and I was wondering what other step parents do about birthday presents. Do I buy him one separately or should the present from his Dad be from both of us?

We buy all presents from the whole family. Cards are non-specific cards, no son or daughter cards just ones they'd like.
They tend to say dad brought me this that and the other (when I chose, arranged and wrapped!) but it doesn't matter to me as long as they like it.

Thanks Sweet, I think that's the best way to do it, but just wanted someone else's opinion :-)