Hey there
Just thought I'd chime in too. My doctor explained that I have a very good chance of getting off of my cpap when I lose weight. He explained to me that the reason he beleived this is first of all women stand a much higher chance of no longer needing their cpap than men do because of the way they tend to carry their weight and women are usually smaller than men.
He said the other factor has to do with how your air ways are shaped and the size of your tongue. If your air ways are very small (and your tongue is large in proportion) it's likely that your apnea is weight related. If your airways are larger (like men tend to be) odds are lower that it's related to weight. Instead it's much more likely that your apnea is caused by other reasons.
This is just what was shared with me, so not sure if this helps or not. But would perhaps support why your other male family members need their cpaps even though they don't have as much of an issue with weight.
Hopefully you'll be one of the lucky ones!
B~