Charlize Theron has seal of approval from Sean Penn's daughter

Dylan told Us Weekly: "They're a great couple. They're both very happy and yeah, I love it. They're both extremely strong personalities and they're very intelligent so conversation lasts between them."

While Charlize sparked speculation about an engagement when she was spotted wearing a ring on her left hand earlier this week, Dylan insisted she has no idea if they are planning to tie the knot.

She said: "I don't even know. I have no idea."

But asked if she would welcome Charlize into the family, an enthusiastic Dylan replied: "Always. Sure, why not? If it's meant to be."

And the model was equally enthusiastic about a sibling for her and brother Hopper, 20.

She enthused: "Always. The more the merrier."

It was previously claimed Charlize - who has two-year-old adopted son Jackson - is keen to adopt a child with Sean shortly after they've exchanged vows.

An insider said: "Charlize always intended to have another child."

Sean has also been bonding with Charlize's young son.

The insider added: "He is a father figure to him."