Having brothers or sisters can make all the difference in your relationships.

Many people understand that the marriage they observed between their parents has an impact on how they later relate within intimate relationships and that they may subconsciously choose a partner who resembles one of their parents, for better or worse. However, fewer people introspect about the impact of their siblings in terms of later relational functioning and mate choice.

In fact, when I discuss the impact of sibling dynamics in sessions with clients, most of them have never even considered this variable, even if they had years of prior therapy! This post lays out how your sibling dynamics may affect your marital dynamics, in both positive and negative ways.

First, the impact of birth order needs to be considered, which is a more common topic in the popular media. In another post, I say:

The best pairings are between kids of different birth order. I would imagine this is because of the imago theory, where each child gets used to interacting with his or her sibling and unconsciously may replicate this pattern in adult intimate relationships.

Since oldest are often more achievement oriented and rigid, and younger are more amiable and flexible, in a marriage between an oldest and a youngest, both partners may feel comfortable with their familiar sibling dynamic recurring in the marriage.

This is accurate based on what I see in practice. Remember, imago theory means that you are drawn to a partner like your caregiver (here, like your sibling), and you fantasize about changing them in ways that you could never change your caregiver.

Combining this idea with the individual personalities of siblings and their unique dynamics provides even more information about how later relationships will go for the siblings in adulthood. Here are hypothetical ways that this can play out in a family with three kids, Joe (10), Jill (8), and Jane (7).

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As you can see from those hypothetical vignettes, each of those characters would find introspection and therapy to be less than useful if they didn't focus on their sibling relationships in addition to what was going on between their parents and in their individual relationships with each parent. The sibling relationships are often even more intense than those between parent and child, as siblings spend more time playing together, especially if they are close in age.

Here are some questions you can ask yourself, journal about, or discuss in therapy if this area seems interesting to you:

Hopefully, this post gave you a new direction to explore to understand your marriage at a deeper level. Couples counseling that has stalled can also be reinvigorated by new topics to think about.

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When you understand why you are responding to your partner in certain ways and what you may subconsciously be trying to elicit by acting the way that you do, you can finally get to the root of the issues and learn new, healthier patterns.

RELATED: The Brutally Honest Way Your Birth Order Affects Your Relationships

Dr. Samantha Rodman Whiten, aka Dr. Psych Mom, is a clinical psychologist in private practice and the founder of DrPsychMom. She works with adults and couples in her group practice, Best Life Behavioral Health.