For Your Adoring (albeit Critical) Mother
"If your mother doesn't tell you the truth, who will?" is her favorite motto and her justification for every criticism every other day of the year so why would this one be any different? She will not lie to you, if she hates your gift she will remind you of it for many years to come. Good luck.
For the Matriarch of Your Family
This is the only gift that matters. The matriarch will steer the conversation over dinner so it is of utmost importance that you buy well. You could lean on your parents or go halfsies with your sibling but either way make sure you get something she really needs. She's lived a full life and the last thing she wants is more junk like a t-shirt that says "I love Grandma" from the Wizarding World of Harry Potter. A bad present is a sure fire way to get written straight out of your inheritance.
For Your Sister Whom You Love but Who Also Knows Just How to Push Your Buttons
It's her world and you're just barely visiting. In fact, you're lucky to even get a word in edge wise but if you do choose carefully because you never know what will set her off again. Peace may be hard to come by in this arena but it's a war worth fighting.