how to call the first and last children in the family? are there any special words for them? an instant, there are some words we use for the last member of the family in Persian, like "tah-taghari", how about in English
Yes, the first one born is called "firstborn" and the last one born is called "lastborn". It's nothing crazy or difficult to learn.
P.S. Omi Di, I think your question asks whether there is a one-word noun in English to describe the first child and last child in a family. My answer is fine albeit a little outmoded. There are nominal phrases, open-form compound nouns, or adnouns to describe this phenomenon that may be better than my outmoded forms:
"He is the oldest / youngest (child). (This can only be used when one has more than two children.)
"He is the older / younger (child). (This can only be used when one has only two children.)
I'm sorry for the confusion. Read J.R.'s answer below about how this can be used; however, I disagree with J.R. that they are "true" nouns; in my personal opinion, they are "adnouns" or even "nominal phrases"; and one could even argue that they could be used as compound nouns in open form, but it's hard to see "oldest" as a true noun when no dictionary calls "older" as a true noun. They are both acting as nouns in some instances and are derived from the superlative and comparative forms of the adjective "old" respectively. Since I go by a far-right presciptivist mentality, i.e., the Antonin Scalia of the responders on this site, I am probably in the minority on this issue. Regardless, my answer has been homologated by the powers that be on this site even though it may be a wee bit antiquated.
Take care and good luck!
Although Nick’s answer is technically correct, it should be noted that firstborn isn’t used very often (it has an almost antiquated ring to it, much like the words sired or begotten), and the word lastborn is even more out-of-use.
The more commonly-used terms are simply oldest and youngest.
A quick look at this ngram supports my point:
At first glance, it may appear as though “my firstborn” is the most common term of the four. However, if you look at the results of these hits, you’ll see that most of these book are actually biblical quotes, such as:
It obviously interpreted Psalm 89, which we read in a previous chapter: “He shall cry unto me, Thou art my father, my God, and the rock of my salvation. Also I will make him my firstborn, higher than the kings of the earth.” (Psalm 89:26-27) (Source)
whereas the hits for “oldest child” and “youngest child” are found in quotes with more contemporary language:
Rather than crying over spilled juice, I patiently wipe it up. Rather then yelling about the sticky hands in my hair and the jam all over their faces, I look at my oldest child — now almost eighteen, almost grown — and remember the days she did the same. I remember that broken crayons can be replaced, but broken spirits may never mend. (Source)
These results would be even more skewed if you take into account how we often don’t include the word child when referring to our oldest and youngest, and instead use the superlative words by themselves: