Not that much you can do about it as babies do cry.
* get to baby as soon he start stirring before he start to cry
* have feeds ready
* separate the rooms from each other as far as possible
* close the bedroom doors whilst using baby monitors

Unfortunately, it may take an adjustment period for your 2 year old to fall back asleep. If you can and you have one, have your partner help your 2 year old back to sleep while you settle bub or vice versa.

maybe bub is going through a growth spurt and waking up for more food but sees the sibling and wants to have fun.

maybe leave a gentle dim night light on for them so bub might settle again vs crying in the dark

Do they sleep in the same room? Try and have music playing as soon as the baby awakes so the toddler can hopefully stay asleep. Maybe if you have room try and get them to sleep in separate rooms it may help

Try playing soothing music.
Our youngest was always waking his sibling & it was a nightmare having 2 screaming children in the middle of the night & the toddler was always the hardest to get back to sleep.
We played soothing music on very low so it wouldn’t cause a disturbance & after we started that our toddler never woke to baby crying & woke up a lot happier in the morning. I’m not sure if it helped her have a better sleep but that’s what worked for us.
Best of luck 🙂

Admittedly I don’t like the idea…but do the children sleep with their doors shut?? Do they sleep close to the same wall?? It is surprising how the noise penetrates through interior walls. If your 7 month old waking for a feed or especially in a warm room a drink? My cousin used to have a bottle or drink ready to give as soon as they heard the baby stir? The drink of water we kept at room temperature overnight. This is one time a baby monitor is handy. I am a light sleeper and used to sometimes hear our baby stirring as she started to wake up. She never slept in our room either – except when she was genuinely quite sick. Avoid using a permanent night light that shines into their rooms too much if you leave their bedroom doors open. In fact some eye specialists reckon they are not a good idea.