If you are concerned then I would voice my opinion. I
have done it mamy times with a sibling joining the group. We
can only tell you our experiences, but if you are not comfortable
you should look for an older baby.

I wouldn't worry about this small an age gap. An experienced nanny can handle that easily and as the children grow the gap will seem smaller and smaller.

Like PP said, you are not at the interactive play stage. You children do parallel play. By the time you get to the age that it matters they would both be old enough.

It's an age difference of only six months and nine-month-olds don't do interactive play anyway. You're overthinking it.

Op here. Thanks for the input.

I know siblings make it work but I guess we had hoped we could have a playmate for our kid instead of a 'younger sibling' type relationship. But thanks for the input. Have to think about it a little bit but maybe it's fine.

It's fine. 3 month old can go in a sling and be carted around to follow the 9 month old.

There are always going to be challenges with multiple kids. If they're the same age, it's racing after two toddlers who are heading in opposite directions. If one is younger, it's trying to wear the baby while helping the other learn to walk (have you ever tried to walk hunched over holding onto a toddler's hands while wearing an Ergo? tricky!). You get the idea.

Many, many families have two children (or more!) and none of them are "held back" by having a younger sibling around. If your nanny feels capable of handling the two children, I wouldn't worry. IMO this age difference would be ideal (they're at different enough stages to make wrangling them easier but close enough that once they're toddlers the little one will be interested in attempting things the older is doing) but again, it's what YOUR nanny is comfortable with.

We are considering starting a nanny share with our excellent nanny who had multiple child experience. However, we have a very active almost 9 month old and our nanny has been talking with a family who has a not yet 3 month old.

Is this age difference too great? I am concerned that an infant requires far more care while at the same time our child needs more supervision as he gets into things (ah, exploring!). And soon he will be ready for different activities that a 6 month younger baby might not be ready for.

If you have experience with this, I would like to hear your opinion. Is it not an issue? Will it hold our baby back? Will it become more of an issue in a few months when our child is walking?

Thanks in advance for any input. I want to make sure the situation is best for our child AND our nanny.