Hello, my friend. Your Nicki looks a great deal like a kitty my daughter recently added to her house of kitties. Her newest one is Cinco, his name given by the lady who's allergy prevented her from keeping him. At any rate, Nicki and Cinco look remarkably alike.
Sounds like Nicki could easily "rule the roost" but he also sounds like a real sweetheart, allowing the other kitty to "nurse" on his stomach like that. We had brother and sister kitties when I was a kid and the female would nurse on the male's tummy; his tummy ended up being a brownish color where she nursed on him. He didn't seem to mind at all.
I really hope with all my heart that your kitties live with you for many, many years. I understand the feeling of loss, in fact, I've had too much of it. I pray you and your kitties have many warm and sunny days filled with love, health and happiness and may you be blessed beyond your greatest dreams.
My love to all,
Jim Grayson
Lexington, Kentucky
USA