I have to agree with just about everything everyone has said. It can be
very difficult. But it's not impossible to train 2 (or more) pups at the
same time. Though a lot of it depends on just how trained you want them to
be. If you're training for show, you're going to want a lot of help
eventually. You'll probablly want help even if just training for "pet", so
get the whole family invested in getting them trained properly now.

As for gender aggression in terrier.. i can also atest to that. 2 years ago
we took in a 4 year old JRT. Her owner was going off to college and her
parents told her she needed to get rid of the dog or they were going to
shoot it (so we were told, anyway) because they wanted to get a rotweiller
(really hope they didn't....)
Anyway, we took her in. We already had 2 poms (my breed of choice) one 8 yr
old male and one 4 yr old female, both also rescues of one sort or another.
Our female pom, Pepe has always considered herself the ruler of the roost,
she is very spoiled, but completely harmless (her teeth are so dull she
cna't even chew through a plastic bag..) They seemed to get along just fine
for the first few hours. Then, while we were all in the living room, the
JRT, Willow, turned on Pepe, grabbed hold of her throat and just started to
shake her. Thankfully we were right there and managed to seperate them
almost immediately, but Pepe had some serious bite marks on her neck and
chest. I will tell you, hubby was so upset by this behaviour he nearly
wanted to shoot Willow there and then himself....
Neither of us had had experience with terriers before (outside of the
neighbor's fox terrier/chihuahua mix..) so weren't really prepared for this.
Needless to say, Willow was never left alone with either of the other dogs
for a good long time. She learned very quickly that biting us or the other
dogs was a BIG no-no (she also used to try and bitw when we'd look at or
hold her feet for nail trimming,,,) and hasn't done it since. She'd been
use to being the only dog and has serious alpha-female issues, and Pepe was
just being her normal "queen of the universe" self and they needed to settle
the pecking order.. Currently, they both think they're #1 and mostly ignore
each other, though Willow will lick Pepe's face once in a while, and I've
had no concerns with leaving them alone loose together after the first few
months.
So it is something to look out for, but alot of it will depend on the
personalities of the dogs involved.. with any luck, you won't have any
confrontations.

Davina