Sending 2 of the same email to the same email address

We provide services to children. Our clients are parents of children. When a parent registers their child into a program, an email is sent out confirming registration. When a parent registers their two children into our program, our confirmation email will only send an email regarding one child to the parent. It won’t send the email regarding the sibling as it thinks we are spamming the client. The email is different in that it names each child.

Is there a way around this?