There's a sort of sibling moratorium when you're establishing yourself as an adult. So much of your energy has to be focused on other things like work and kids. But when people become more settled siblings tend to regroup because now you're building a new extended family.
Because I am not formally trained in the medical sciences I can bring in new ideas to AIDS research and the cross-fertilization of ideas from different fields could be a valuable contribution to finding the cure for AIDS.