That depends somewhat on the local climate, and California has a wide
range of climates.  Basically, the breeding season starts in December
in the warmer areas and continues through perhaps August.  Gestation
takes 60-67 days - figure March-April as the time for a peak in kitten
births.  It takes another three months or so for the kittens to be old
enough to rehome, though some people give them up as soon as they are
weaned - figure May through July as the peak time for kitten
availability in the temperate northern hemisphere.  Of course,
strictly indoor cats aren't influenced as much by the climate as
outdoor cats, so you could start seeing kittens on offer in a couple
of weeks.

There are no kittens on offer here, but pregnant gueens are, so
kittens *are* on the way.

I'm not so sure that early bonding means all that much: I have three
sets of sibling pairs and I don't notice any special relationships -
in fact, it seems that the cats actually spend more time with and are
more closely bonded with unrelated cats, or they are loners.  The
closest associations seem to be between small cats and very large
males: Tigger and Fleagor are most often accompanied by some of the
smallest males and females.  Millie seems not to like her brother Ozy
very much, but she likes to be with Fleagor; Dandy doesn't appear very
friendly with his sister Maryweather, but loves Fleagor; Ozy,
Maryweather, and a couple of others like to use Tigger as a pillow;
Avery and his brother Mudpie do hunt together, but otherwise don't
spend any time together.  Maybe a large (neutered) adult male now and
a smaller and younger cat (either sex, but fixed) in a month or so
might work out well.  Or not, but that's the problem with siblings
too.

T.E.D. (tdavis@gearbox.maem.umr.edu - e-mail must contain "T.E.D." or my .sig in the body)

Why not adopt an adult pair? So many need good homes these days especially
with cat and kitten season now in the beginning stages.