Dear Erika,
I know, that whining is wearing, isn't it? I still remember the whining days with my children and they are grown up now.
I think that it may have to do with two things. His age, for one, and probably he is feeling a little insecure because of the baby. I know that those 8 month olds are the cutest in the world. So he can't help but love him, and also feel a bit like he wasn't ready to share Mom and Dad.
It's o.k., you are doing all of the right things and if you stop paying attention to it, he will eventually stop. Don't say one word or react in any way when he whines, but find something to take his mind off the object of the whining. If that doesn't work, then walk away, but not too far away. You want to know what he is going to do next.
I notice that as I get older, I whine some too, I think that it is because I have been through so much in my life that I am tired out. So those are two different reasons for whining at opposite stages of life. I never have gotten my way when I whine, so I am trying to stop. You never get too old to make yourself a better person. I always say that on the last day of my life, I will make a huge mistake and I will learn something new. Life is a wonderment.
I am so glad that you have two boys, they will be the best of friends in later life and support each other like no other person can.
Sincerely, C. N.