I’ve been a care giver for my mom most of my adult life. I’ve put it down to having a 12th house sun (service & sacrifice).

Oh I forgot about my 12th house Sun. Mine has played out in sacrifice and confinement.

How about a 12th house Moon?  Or 12th house outer planets transits? 

I was just thinking it feels like the roles have changed, especially with my mom. It feels like I'm the parent now.  Pluto is transiting my moon. My mom is dependent on me emotionally now, as well as physically. Somedays it feels like a Pluto thing. She can get really down some days and say hurtful things. Thankfully I've developed patience.  I used to be lacking in it. 

I'd say Saturn transiting the 4th house or even 10th house indicates the possibility of increased responsibilities regarding caring for a parent especially if age-wise it's coming (e.g. parents in late 70s.)

Mentally the switch to more caregiving in a person's life might be linked to progressions...and then transits might bring about the event of more caregiving required perhaps...

Natally I'm thinking Saturn/Sun,  Saturn/Moon and Saturn/Venus conjunctions...12th house luminaries...Cancer luminaries...Capricorn luminaries...stelliums in the 6th house...some ideas jumping in my mind.

This is a very interesting topic and question. 

Pluto-Moon transits can be really tough. Because the moon represents the mother, it can certainly bring some hardships in this area. I can fully understand how this can be a challenging time for you, Maria.

Cris mentioned transiting Saturn on the parental axis. This makes sense to me. Since my last post, I have been thinking about how my natal Saturn in 4th, may contribute to my strong sense of responsibility towards family.

Not surprised you've Saturn in 4th Hades Moon, with you being a caregiver most of your adult life.