Fòram na Gàidhlig

Can someone let me know if I have the grammar, lenition, etc. correct? Thank you.

Gàidhlig
piuthar
tha mi a' phiuthar
tha mi a' phiuthar mhor
tha mi a' phiuthar bheag
brathair
tha mi a bhrathair
tha mi a' bhrathair mhor
tha mi a' bhrathair bheag
mathair
tha mi a' mhathair
athair
tha mi an t-athair

English
Sister
I am the sister
I am the big sister.
I am the little sister.
Brother
I am the brother
I am the big brother.
I am the little brother.
Mother
I am the mother.
Father
I am the father.

If it's never been posted here, I've found this chart very helpful in how to use 'the' correctly: http://www.echonotation.com/write-your-own-grammar/ (scroll about halfway down to find the chart)

You're linking a noun and a pronoun, so you have to use 'S mi(se) ... rather than Tha ... And "brother" is masculine so no lenition: am bràthair (mòr/beag).

I'm a beginner as well. This looks like an interesting question to see if I understand the grammar I've been reading about. The challenge for me is always whether I can apply the grammar I've read about to complete sentences. I think there are other options for these sentences and I'm wondering if an advanced learner could comment on these - which option is right/wrong? Also of the 3 options below, is there one that is best (or used most often) in spoken Gaelic (assuming the grammar is correct)? Mòran taing!

Option 1 with 'S e + “a” or “the” (I am a sister. -or- I am the sister.)

’S e piuthar a th’ annam. (a)
’S e a’ phiuthar a th’ annam. (the)
’S e piuthar mhòr a th’ annam. (a)
’S e a’ phiuthar mhòr a th’ annam. (the)
’S e piuthar bheag a th’ annam. (a)
’S e a’ phiuthar bheag a th’ annam. (the)

’S e bràthair a th’ annam. (a)
’S e am bràthair a th’ annam. (the)
’S e bràthair mòr a th’ annam. (a)
’S e am bràthair mòr a th’ annam. (the)
’S e bràthair beag a th’ annam. (a)
’S e am bràthair beag a th’ annam. (the)

’S e màthair a th’ annam. (a)
’S e a’ mhàthair a th’ annam. (the)

’S e athair a th’ annam. (a)
’S e an t-athair a th’ annam. (the)

Option 2 with "Is mise"

Is mise a’ phiuthar.
Is mise a’ phiuthar mhòr.
Is mise a’ phiuthar bheag.

Is mise am bràthair.
Is mise am bràthair mòr.
Is mise am bràthair beag.

Is mise a’ mhàthair.
Is mise an t-athair.

Option 3 with "tha mi nam"

Tha mi nam phiuthar.
Tha mi nam phiuthar mhòr.
Tha mi nam phiuthar bheag.

Tha mi nam bhràthair.
Tha mi nam bhràthair mòr.
Tha mi nam bhràthair.

Tha mi nam mhàthair.
Tha mi nam athair.

they are all correct - it all depends on the context.

Option 2 is what you'd use if you introduce yourself.

Option 3 is a transitory state. For example, when your first child is born, you could say "Tha mi nam mhàthair a-nis!"

Many thanks to all! That's very helpful!