The Hebrew word for uncle is דּוֹד (dohd); the word for aunt is דּוֹדָה (doh-DAH - more commonly pronounced DOH-dah).
Why? Because the word דוד itself means dear one - aunts and uncles are people close or dear to a child (i.e. close enough for love and gifst but usually distant enough so the kids don't get disciplined by them).
The word for grandmother is סָבָה (sah-VAH), but the far more common word is סַבְתָּא (SAHV-tah). Likewise, סָב (sahv) is the proper word for grandfather, but סַבָּא (SAH-bah) is much more commonly used, as in, סַבָּא שֶׁלִּי אָמַר לִי לָרוּץ כָּל יוֹם (SAH-bah sheh-LEE ah-MAHR lee lah-ROOTS kohl yohm) - my grandfather told me to run every day.
Why these words today? Well, today I'm a דוד (sounds much better than uncle to my ears), my sister is a דודה, and my parents are סַבִים (sah-VEEM).
That means my brother is an אַבָּא (AH-bah - father) and my sister in law is an אִמָּא (EE-mah).
מָזָל טוֹב! Mazal tov! to the happy parents, grandparents, the whole extended family... and to the דודים!