I grew up in India. My parents are Indian and English so this already set me off on a path of speaking multiple languages. I got two languages from my father and friends and one from my mother. India has over 1500 dialects and 22 official languages. I speak 3 of them - English, Hindi, and Marathi; and because of this I can understand a few more due to their relation to English or Marathi. A bit like how French and Catalan and Spanish are connected or how the Spanish can understand the Italians and vice versa.
I would speak Marathi with my siblings, friends, father and grandparents, English with my mother and her relatives, and hindi with other friends and locals. You might think this can get confusing as a child however from my experience I never felt confused between the three languages. However, from my memory, it was anything but confusing. Really easy to understand, learn, differentiate, and speak. Sure, I struggled with grammar but the speaking and comprehension was quite easy. However, when I started to learn a fourth language at the age of 16 originally, I found it much more difficult.
I came to realise that as we get older, one thing we lose is adaptability. As a child we are constantly accumulating information and still learning how to compartmentalise everything. Once you are older and have a set way it becomes a lot more difficult to include new information and not get confused or lost. This is what I found when learning a new language totally unrelated to what I could speak.
In my next post I'll talk more about my experiences learning a new language. Stay tuned! ;)