Two films by director Florian Zeller, which I will briefly comment on in one post because I'm feeling lazy.
In general, they are not similar in terms of plot or atmosphere, but both are family dramas, and quite powerful ones at that.
“The Father” seemed interesting to me because while watching it, you try to understand, roughly until the middle of the film, who is actually crazy in all of this – the old man, his relatives, the director, or you. In the end, it turns out that it's you, since you're still watching with interest. But in the end, the film doesn't leave an open ending or a feeling of incompleteness, as sometimes happens in such psychological mind-benders; instead, it leaves behind a feeling of sadness and compassion for what is happening.
I watched “The Son” first, and looking back, it's better to watch it in that order. No, there is no plot connection; my recommendation is based purely on some script and directorial nuances.
spoiler
To be more specific, after watching “The Father,” you might accidentally spoil the explanation of what is happening at the very end of “The Son.” This is a soft spoiler, but it might slightly spoil the impression, I think.Well, that's all... Enjoy watching.