This is just one of the many questions I have had difficulty answering from my two and a half year old as we count down the weeks to our new arrival.
There is much advice around on how to break the news to your children that there's going to be another baby in the house.
But I can't help thinking that my son is actually the least stressed or worried about the impending birth at the moment, 24 weeks in.
He's looking forward to bossing his little brother around and teaching him to talk, walk and hand over all his toys and food on demand.
His parents on the other hand, while looking forward excitedly to having a new member of the family, have gone into a kind of slow motion meltdown as the due date approaches. We've suddenly realised just how much we have to do beforehand.
The thing about babies is the bewildering amount of stuff they seem to need. For any parent-to-be there's a point at which it seems as if you're trying to kit out some travelling Royal household of the Middle Ages or putting together all the requirements for a space voyage to Mars.
We're lucky enough to already have things like a pram from last time around. But there's a panic as we try to remember exactly who we gave various thing to like the Moses basket, steriliser and all those clothes.
Meanwhile we have a room full of other stuff brought back to us from friends and relatives, that I don't even remember us having in the first place. And given how long it took us to put together the Jumperoo, a baby bouncing device that proved a hit with our first child when he was a baby, I'm not sure we wanted it back.
Along with the sudden, expensive realisation that we many need a bigger car we've also shelled out on a new, bigger bed. This is not just because my wife's growing bump is making sleeping harder for us both – but because we know from bitter experience that both trying to share a bed in the middle of the night doesn't work well with breastfeeding at all hours.
Last time round we ended up topping and tailing like the grandparents in Charlie and the Chocolate Factory.
Meanwhile my wife, who had been largely enjoying the second trimester, has started suffering with varicose veins and is convinced that her legs will never go back to looking the way they did before.
Dads, like me, are often left tongue tied as they try to know what to say to their partners whose bodies are doing increasingly bizarre things during pregnancy.
All I could do was dredge up a bizarre pregnancy trivia fact I'd heard, saying lamely: "Well it could be worse – you could end up pregnant for more than a year." That weird record was allegedly achieved by American Beulah Hunter, a 25-year-old, who, apparently, was pregnant for a staggering 375 days back in the 1940s.
Given the expression on my wife's face, I'm not sure this helped!
Last week the stresses and strains of the bump, including a bout of feeling faint, meant I found her looking a bit tearful.
At this point I sort of looked at my son wondering what to say or do. It was left to him to come up with an answer.
"Don't worry mummy," he said, turning to my wife. "I'll look after you" and gave the bump a cuddle.