In direct contrast with English, there are a lot more distinct terms for describing immediate and extended family relationships. There are separate terms of an elder versus younger sibling as well as delineations of whether the relationship originates from the fraternal versus the maternal side.
Now before I actually start, note that I’m mostly sticking to phonetic spelling of Mandarin as opposed to actual Mandarin pinyin for this post unless otherwise stated or phonetic spelling gets too difficult for me.
So let’s start with the immediate family. Dad and Mum are usually called Baba and Mama in Mandarin. Your elder brother is your Ger-ger (this is the actual pinyin, not the phonetic spelling, I don’t know how to spell it phonetically, I’m not a native Mandarin speaker and I never leant English pronunciation properly with the vowels and consonants either) whereas your younger brother is your Didi.
Now, when it comes to your cousins, the lineage is slightly confusing because the delineation is not just as simple as from the fraternal or maternal side. Rather, the delineation is whether or not the cousin shares the same surname with you. So, therefore, all your maternal cousins and your fraternal cousins who are offsprings from your aunts are considered your maternal cousins or biao (pronounced roughly bi-ao) -siblings as they translate to in Chinese. Only those who share the surname as you yourself and from your father’s side of the family i.e. offsprings of your father’s brothers are your fraternal cousins or tang (pronounced t-ang) -siblings as they are called.
For your uncles and aunts, the system is more similar to siblings. Your fraternal uncle is your Bor or Sue, depending on whether he is older or younger than your father. Your fraternal aunt is your Gu (or Gu-mu if you write it, it’s two characters, meaning “fraternal aunt-mother” if you want a literal translation) and the delineation of elder versus younger can be different across different regions when we speak of it. Your maternal uncle is your Ju-you (this is as close to the pronunciation as I can make it, it’s supposed to be a single character) whereas your maternal aunt is your Yi. Now, just on the topic of delineation of elder versus younger, I think Mandarin mainly uses a prefix of Big/Old and Small to separate the two. Whereas in Cantonese, we usually make use of suffixes. So our aunts who are our fathers’ elder sisters have the ma suffix when we call them (Gu-ma or aunt-mothers in literal translation) whereas our fathers’ younger sisters are called aunt-elder-sisters in literal translation (I can’t even phonetically spell the Cantonese term of elder sister so…). For our maternal aunts, the elder also takes the suffix ma but the younger was called Ah Yi (Ah is just a prefix that you can add to pretty much any name if you have familiar with the person, for example, we usually call our friends by their first names in Cantonese and add the Ah prefix in front). For our maternal uncles, we always add the suffix fu (meaning father) in Cantonese but our younger maternal uncle we add a second suffix with the literal meaning of son but takes on the meaning of little in colloquial use. For example, you can add the same suffix to the term wife or husband that makes it seem more intimate somehow.
For grandparents, your fraternal grandfather is your Yeah-yeah whereas your fraternal grandma is your Nai-nai (pronounced Ni-ai in one sound as close as I can tell). Your maternal grandfather is your Wide-gong (gong is pronounced g-ong, the term is outside grandpa in literal meaning) whereas your maternal grandma is your Wide-por (or outside grandma). In Cantonese, we usually call our fraternal grandma Ah Ma with the inflection going down whereas Nai Nai is what we call our mother-in-laws. We also tend to call our maternal grandparents g’ong g’ong and por por respectively.