3 1/2 month olds still suckling momma cat: Is it normal?

Yesterday, during afternoon feeding I noticed that the 2 babies that are almost 3 1/2 months old still suckle from momma. Momma doesn't mind and even lays down for them to feed.

Since about 4 weeks old they all eat dry and wet food and drink water very well from the dishes.

Is this a behavior problem or is it normal?

Thanks 

If the mom doesn't mind it's fine.  Could just be a bonding or comfort thing.  When she gets tired of them nursing she'll let them know.  I think it's kind of sweet.  Some of the forums are about the mom's pushing their kittens away, so it's nice to hear about the moms who cuddle.

She's the sweetest momma ever. One time she even bought home an abandoned kitten (or stole) which turned out to most likely be sick and didn't make past the third day. But it was still sweet of her to clean him and put him with the (at the time) 7 w/o babies .

She also still licks them clean and they "hang out" around our home inside and outside the house. 

Thanks for replying 

Update: Kid Cats still "nursing" at 19 weeks / over 4 months old 

Saw them still nursing on Friday. Is this a problem? Aren't they a little old to be nursing? 

I have a mom cat and her two kittens - one of the kittens nursed for almost 5 months - right at the age yours are at now!

The other kitten stopped much earlier.

So it really depends on the individual kitten - and of course, the mom, as long as she doesn't mind, so nothing wrong here, everyone will move on once they are ready - either the kitten will stop, or the mom will make him stop!  

UPDATE: 

The kitties turn 5 months this Thursday and they are still suckling! I'm amazed at this   

Wow.  I'd be like "Get. Off." 

Hahaha.. yeah! I find it endearing though. It's really nice to see them so close 

UPDATE:

Saw the fluffy butts still suckling on momma on Saturday. They turned 6 months old yesterday. Seems strange to me that they are still suckling at this age