The phrase "oldest grandchild" refers to the eldest or oldest grandchild among all the grandchildren. It means they are the first-born grandchild in the family or the oldest among their cousins.
Sentences with «oldest grandchild»
I'm a 63 - year - old grandma who retired early to care for my now 3 and 1 year old grandchildren. (babycenter.com)
You may want to volunteer to go on college visits with older grandchildren. (thespruce.com)
Also, this type of campaign typically targets older grandchildren, and forcing visitation can be difficult. (thespruce.com)