Starring opposite Mark Wahlberg, Byrne stands out as Ellie, who wearily adjusts to an intensive mothering role.

But Byrne says this experience was a different one.

Read on below.Instant Familyis now playing in theaters everywhere.

Instant Family

Credit: Hopper Stone/Paramount Pictures

ENTERTAINMENT WEEKLY: Why did you want to get involved in this movie?

ROSE BYRNE:I’d just had a baby, so I was super emotional.

[Laughs] I read the script and was just sobbing.

It was so moving and heartbreaking.

I’d never seen anything or read anything like it.

I jumped right in.

What did you learn about foster care?

I don’t know where to begin in terms of what I learned.

I was really naive about the foster care system.

But I met incredible families and social workers and kids who’d been in the system.

I don’t even know where to begin.

Any specific anecdote you’re able to share?

I had a fantastic dinner with an incredible group of mothers who’d fostered children.

I’ll never forget it.

The movie has a balance, where it’s funny but not overly so.

How did you strike that balance?

I was absolutely nervous.

I was worried about the tone: how far to push it, how to ground it in reality.

This was Sean’s story, so I trusted him.

I knew how passionate he was.

We’d push the comedy and then pull back.

It was very collaborative, finding that line.

Because it is a fine line.

It’s a very fine line.

I remember agonizing about that.

It took such a long time to figure that one out.

I was asking, “What am I really saying?

Why is it funny?

How should I play it?”

There’s also theadoption picnic, which from this viewer’s perspective was almost surreal.

I’d never seen an event like that.

I couldn’t believe it.

I was like, “This is real?”

Sean said, “Yes, this is what we did!”

It was one of my first questions when we talked on the phone.

Just so strange that this happens.

You’re a mother now, as you mentioned.

Did that inform how you approached this material at all?

The kids in the movie are older [than mine], so there are different challenges.

But there’s a universal thing, once you’re a parent, that you get.

[Laughs] That reminded me a lot of when I was a teenager.

This is being released in time for the holidays why is it a great movie for the season?

It’s about families and what they look like.

There’s no one way a family should look.

They’re of all sizes, all creeds.

So it’s genuinely meant for everybody.

At a time when families are being torn about, this is about a family trying to come together.