Behind the wall of my living room is my neighbor’s Buddhist altar. Will this have any impact on my family?

No impact! In other words, there are only good effects and no bad effects. Specifically, wherever there are Buddha statues, there are dragons and heavenly protectors, and there is a kind of positive energy. If you are close to the positive energy, of course it is good.

It seems that you have not had much contact with Buddhism. Each has its own causes and conditions. When nothing happens, just pretend that the Buddha statue in your neighbor's house does not exist. This will not have any impact on you. When there are problems that cannot be solved by human power, if you If you are willing, you may wish to pray in the direction of your neighbor's Buddhist shrine and pray for Buddha's blessing.

In short, making offerings to Buddha at your neighbor’s house is only good for you, not bad.

Note: I have been exposed to Buddhism for many years. Of course, I dare not say that I am a beginner.