Suddenly had a thought ruminating around my head, that if one was going to or has kids and plan to teach them multiple languages, what would be the best choices? I mean ones that when learned, would offer quite a breath of sister languages and you would have help with plenty of writings as well.

So thinking about it I came to English, Russian, Japanese, Arabic and Hindi.

I picked English because it is my native language but you could go with French or any other Romance or Germanic language if that's your native. Also Chinese can be an alternative. I also picked Japanese because it has more flexibility in it's application of Kanji given how it modifies.

So I narrowed it down to those five because you have the options of the Latin, Cyrilic, Kanji and Arabic writing which opens up so many readings here. There is a lot of shared vocabulary there as well as Steve mentioned with Czech, Russian and Polish and Ukranian. I assume the same holds true with Farsi to Arabic and possibly Turkish. The Arabic script is it's writing which Farsi has as well.

Lastly while there is definitely different writing style in Hindi I am pretty sure there is similar vocabulary.

My thought was teaching those five to native speech if possible would make the sister languages take even less time to learn should the child desire to learn those others later.

I don't know if anyone here has thought of this or know someone who has raised their kids learning those languages or something similar.

I am not discounting Indigenous languages that may not have a writing system or ones in general that don't. This was more a ponderance on those that are the most prominent alphabets and have the largest variety of written work.