Let me second Kevin's "Welcome!"
I am also married with OSO - a hinge in a MFM Vee - and have been poly since before they had a word for it). Neither of my boys is seeing anyone else (although I anticipate Dude will at some point).
The three of us live together. During the early months I struggled with keeping things "balanced" as well. This has lessened over time as I slowly internalized the concept that "fair" =/= "equal". As long as I am providing each relationship with the care and attention it requires I am doing my part. Each person has their own wants/needs to be addressed...and these are not the same for each.
Me: poly bi female, in an "open-but-not-looking" Vee-plus with -
MrS: hetero polyflexible male, live-in husband (together 21+ yrs)
Dude: hetero poly male, live-in boyfriend (together 3+ yrs) and MrS's best friend
Lotus: poly bi female, "it's complicated" relationships with Dude/JaneQ/MrS
TT: poly bi male, married to Lotus, FB with JaneQ
VV and MsJ: bi-women with male primaries, LTR LDR FWBs to JaneQ
My poly blogs on this site:
The Journey of JaneQSmythe
The Notebook of JaneQSmythe