Often in sharing what polyamory is like I have invoked the analogy of having many children and loving them all the same amount but differently in terms of what works best as one interacts with each child. Having multiple lovers is very much like that, I would say. In the perfect scenario, that's the case but not always. Still it is a reasonable analogy that makes sense to someone new to the concept of polyamory.
In the last year I have begun to welcome grandchildren into my life. It occurs to me that this life stage is an excellent analogy for compersion. I have two grandchildren who I only became aware of months after their births as their mothers are no longer girlfriends of my 22 year old son. (Yes, one can preach safer sex but that doesn't mean anyone listens.) Both moms and babes live with the mothers' parents and they are the primary grandparents. I have mediated for our family's involvement and see them occassionally and not nearly enough but schedules are like that and as a poly person I get that and inclusive extended family a bit better than the average bear. Still being a secondary grandparent in terms of access is a tough one.
Recently, I watched another son and his girl friend work together with maturity beyond their eighteen years to bring a beautiful baby girl into the world. They were supported by her mother and the midwife for most of it with a doctor and nursing staff addressing the actual delivery. I was not present for the actual birth but helped spell them off in support of her contractions and I got the first photo of the newborn. I remember very clearly the birthing of my children and this was a rather surreal third party experience. I'm so proud of my son and his girl friend who I have long viewed as a daughter. I'm happy for them and can't wait for my next snuggles. I'm happy that my son is surrounded by so much love. I did feel a bit left out. My baby having a baby and all that but I was most privileged to be involved as was needed.
The analogy to compersion comes from being head over heels in love with these three amazing children and having to stand back as I'm not the parent and not the primary caregiver. I'm also not the only grand parent nor the one with the most access and availability. I'm happy that they are loved and well tended. I love them and can't wait to spend time with them. Compersion is being happy that your lover is being loved by someone else they love. It goes beyond sharing to being happy that someone is loved even if it isn't you doing the kissing. Grandparenthood in a nutshell. Being so full of love and bursting for that dear little baby that your heart overflows to see the look on their parents' faces at each new wonderment and you cry with joy when you see the other gramma do it. Compersion.
Just when you think you can't possibly be happier - a cute little face looks up at you and your heart explodes. Life is very very good.