Im a firm believer in that two cats are better than one.  If you google it,
you'll come up with a lot of sites that recommend it too.  Gender doesn't
matter much.  at this age it is still all like a sibling to them.  But do
get them neutered as soon as possible (im a fan of pediatric neutering but
not all vets do it)

Most cat people recommend at least as many litter pans as cats.  The
only thing I see wrong with your plan is that seven weeks is *way* too
young for a kitten to be removed from its mother - twelve weeks is
about ideal.  Kittens tend to get along quite well, and continue to if
they are raised together.

I'd suggest a boy kitten just for the slight personality differences and
I'd *strongly* suggest getting them both fixed at 5 months.

Two cats are actually less work than one.  If you get them as kittens
(which you have) you don't need separate litterboxes as that's how they
will be growing up.

pat

I got my first kitten July of last year. After 3 months of constant demands
of  play and attention every waking moment of the day I adopted another
kitten. There was around three month difference in age, no problems. I
brought the new kitten Comet home, put him (they are both fixed males) on
the floor in front of Gizmo who began growling and hissing, they circled
each other then went to opposite ends of the room. I grab my coat and left
the house for a couple of hours. When I returned they had sorted thing out ,
sort of. Within two weeks they were playing with and grooming each other. I
could finally sit in my chair in reletive peace, cats will always demand
attention, to read or watch T.V.
Two litter boxes are ideal, you can clean one and leave the other for the
cats to use while the other is out of commision.
Do get your cats fixed. When Candy reaches sexual maturity she will drive
you crazy howling and trying to get out and every male cat in the area will
be at you door step trying to get at her.