SOLVED. Probably Middle Grade novel about fraternal twins, each chapter alternated their POVs, the title had something to do with the saying "two peas in a pod." [s]

[Tina]

I read this probably in 2016 or 2017, their grandfather was an important figure to them though he may have died. They had to get used to no longer doing things together for some reason I think. The weather wasn't great. Might have been some train tracks or some sort of secret hideout. I think the boy was more withdrawn than his sister. The book might have been a diary gifted to them by their grandfather but I could just be misremembering. I believe the cover was blue with the title large at the top and two small drawings of each twin at either end. Maybe a picture of some peas in a pod.

[Anser]

Perhaps Jake and Lily by Jerry Spinelli? They're twins who had this subconscious connection where they could feel what the other was feeling, and they would both sleepwalk(?) to the train station on their birthday every year. But as they get older they start to drift apart and lose their ability.

[Tina]

Oh my gosh yes, that's it!! Thank you so much!

[Kris]

Glad you found your book, Tina.
Jake and Lily by Jerry Spinelli - Anser's find.