My youngest sister was more comfortable with watching and helping right now, which we were both fine with. We knew that sometime - soon, from the looks of it - she’d start touching us, and rubbing, and enjoying us too.
My sister came to me when she first started thinking she might be bisexual - for obvious reasons, since I’m a lesbian. I told her that the only way to know was to try things out and see what you liked. We haven’t stopped trying things out since then.