I took care of an autistic child for a while, it was a big challenge, I had difficulty, but I learned a lot about understanding how an autistic person's mind works.
My roommate here in São Paulo has autism as well, and we made a beautifull friendship.

We also have new members in the family, my brother recently had twins, a girl and a boy. I spent the first 4 months helping my sister-in-law with the newborns. It was also a great challenge, as it requires great delicacy and patience to understand their needs.
I also have a 4-year-old niece, I took care of her for some weekends, she live near me, so when I can I go stay with her.
Another experience is with teenagers, in my 19 years to this days, I take care of my 16 year old niece, and I believe it is a bigger challenge of all, because at that age they are going through so much, their heads are so confused, and it is a time of discoveries and frustrations.