It was part of the reason I have two, because I had a sibling and it's a nice thing, to have a playmate at home on hand. As long as they're in a good mood.

I think there are pros and cons and you just need to keep thinking about it. For us, #1 could have done really well as an only child, but far out I'm glad #2 has his big brother, he's sooo social. Whenever #1 is out somewhere #2 is all over me - so sometimes (okay, often) they egg each other on when being naughty, and get cross and make each other cry, but often they entertain each other too and watching them play makes me glad there's two of them...even watching them fight makes me laugh.

Having said that, that's just my experience. When I take just #1 out by ourselves man, it's sooo much easier than having two! So there are definitely upsides to one.
Like I said, pros and cons for everything, you just need to decide how the balance is in favour for your family. I don't think there's any rush. xo