Kona's relationship with his Mommie pretty much stabilized shortly
after I adopted he and Sebastian last year.  Kona began occupying my
lap immediately after he began living in his new home and he likes
being in the same room with Mommie even when he's not in my lap.

Sebastian's relationship with Mommie has been slower to develop.  
Kona resents my giving Sebastian attention and tends to try to horn in
whenever Sabastian gets some lovin'.  That has seemed to bother
Sebastian in the past.  But Sebastian has become less concerned about
Kona's objections recently.  He's become much more of a lovebug,
rubbing my legs, purring for short periods of time when picked up,
sleeping in the bed with me, and generally being a lot more
interactive even when Kona's present.

If I were a psychiatrist, I would say Sebastian had a breakthrough
this week.  After work, I plopped down in a chair on the living room
and stretched out my legs, setting my feet on the ottoman and started
to watch TV.  Sebastian came in and after he did his usual "patrol" of
the area, he jumped in my lap and started purring and kneading.  He
did this for about five minutes, then he settled down longways on my
upper legs and actually went to sleep there. This was a first for him,
in the past he has wanted to be held or sit on the lap only for a
short period of time, although he wants to be close to me.

About the time Sebastian settled down to go to sleep on my legs, Kona
lumbered in.  He looked up and saw that "the lap" was occupied.
Naturally, he was not pleased.  He jumped up on the cat cactus sitting
a few feet away facing the chair.  Now, Sebastian at 11 lbs is just
about a perfect fit for the cactus but Kona at 17 lbs+ just can't fit
all of himself in-there's always at least one leg sticking out as well
as some excess Kona spilling over the sides. Kona is not fazed at all
by this lack of decorum.

Oh, the glaring!  Those huge eyes stared at the fluffy black cat in
"the lap" and never blinked. If looks could kill, Sebastian would have
been a goner.  But Sebastian was so relaxed that instead of going off
somewhere, he just nestled down.  Sebastian snoozed while Kona
continued to glare.  For an hour.  I don't think Kona blinked once.

Finally I just had to answer the call of nature so I gently removed
Sebastian and told him what a sweetie he was.  He stretched out,
apparently none the worse for having been the object of Kona's intense
disapproval for over an hour.

I have a feeling that some sort of timeshare arrangement is going to
have to be worked out.