Yes there is.
моя is for feminine nouns
and мой is for masculine nouns
You may notice that there is much overlap between the most common noun endings and the endings of "мой". It is not perfect but makes memorizing them a bit easier, I guess:
- моя кошка, моя семья
- мой брат, мой клей
- моё окно, моё море
- мои кошки, мои коты
Now, we shall take a look at the past tense. Hmm... let's take the verb "to be":
- кошка была ...
- кот был ...
- яйцо было ...
- кошки были ...
Should we take some adjectives? That's advanced material! The course of English only teaches you "big" after the third checkpoint. But we can do it, right?
- большая кошка
- большой кот
- большое яйцо
- большие кошки
Thanks for the explanation Shady. :)
By the way, is there some sort of page you have where we can ask you questions about Russian? I would love to be able to do so.
No, a native would not (ребёнок and человек are explicitly masculine regardless of the sex of a person they refer to).
what is the difference between дети and ребёнок? (aside grammatical number)
There is none. In modern language дети acts used as a plural of ребёнок. This suppletion is quite similar to "people" being used as a plural of "person" in English (which also has a counterpart in Russian: человек → люди).
What's wrong with ребёнка? It has been translating that word as child all through the exercise