I've done it, nanny family oldest cd was 15mos when their twins were born. I started when ODC was 17mos and babies 2mos. That first year is a complete blur. I don't think I sat down once before the twinnies turned 1.
They were a young family and I was getting back into nannying after a 5yr hiatus. I was paid $2000 a month. Looking back it was practically slave labor wages (40-45hrs a week), plus I cooked dinner for the family every night, straightened the house every day, made all the baby food, and did a curriculum/art projects every week with ODC.
It is by far the job I have the fondest memories of. The youngest twin was my carbon copy shadow by the time I left. Now I watch her grow up in pictures on Facebook and it's been over a year since I've seen her or her siblings, but damn do I still love those kiddos like crazy. I miss them as much, too.