Dear Carolyn: My husband and I are expecting our first child in January. We are thrilled about this and are excited to be parents.

I am struggling because I have a sister seven years older who cannot have children. Whenever I get excited about the upcoming birth, my mother is quick to remind me my sister will never have this experience. I've tried hiding my feelings around them because I want to be sympathetic, but I also don't want to feel guilty for how I feel. It has gotten to the point where I don't even want to include them in the baby shower.

How can I acknowledge their feelings but still enjoy this time in my life?

Carolyn says: Wait — "around them"? And "their feelings"?

If you meant your sister's feelings, then that's understandable (with sympathy, not guilt) — and if your mother issues these quick reminders because your sister is nearby and still grieving and you're missing signals that your sister is losing her composure, then that's understandable, too.

But if you meant that exactly as you wrote it, that your sister's feelings and your mother's are one and the same; and neither of them is able to feel your joy through the weight of your sister's misfortune; and you feel guilt for healthy pleasures; then there's more here than a childlessness story. There's also a story of a mother overinvolved and overinvested in one daughter's emotional life — plainly at the expense of the other's.

Where is your mother's joy and excitement at your pregnancy?

Life is complicated, humans are complicated. We're equipped to hold contradictory thoughts and feelings. Happy anticipation of one child's future can — and does, every day — coexist with sadness about another's.

Some situations interfere with that ability, like depression or trauma. That's why your sister herself gets 90 percent of a pass on this, with the 10 percent reserved for common sisterly courtesy. Such as: "I'm genuinely happy for you, and sorry I'm in such a bad way right now that I can't properly show it."

But, again, when there's no apparent boundary between one family member's feelings and another's, and when the entire family is expected to live and talk and feel utterly in service of an Alpha Feeler, then it's time to start reading up on codependency.

Better yet: Since your family of origin gives off that burned-rubber smell of dysfunction, and since you're at Stage 2 of spinning off into a family of origin for a child, it might behoove you to talk through this guilt you're feeling with a skilled family therapist. The better grasp you have of the history that brought you to this moment, the less likely you'll be to repeat it.

And hey — congratulations. I'm really happy for you.

E-mail Carolyn Hax at tellme@washpost.com, or chat with her at 11 a.m. Friday at washingtonpost.com.