Briana Jungwirth watched the band perform from the side of the stage during the opening night of their London residency at the O2 Arena on Friday (25Sep15), British newspaper The Sun reports.

The U.S. stylist, who is pregnant with Louis' first child, was spotted with the singer's mum and his sister Lottie, who is a make-up artist for the band.

A source tells the newspaper, "Louis and Briana have grown much closer since he found out she was pregnant. He is taking great care of her and has definitely developed feelings for her. He thought it would be a nice idea to fly her over for the gig so they could spend some proper time with each other."

The gig on Friday was the first of six sold-out nights at the O2 Arena, and the band will then continue their tour with stops in English cities Manchester, Birmingham, Newcastle and Sheffield, Glasgow in Scotland, Dublin, Ireland, and Belfast, Northern Ireland.

It emerged in July (15) that Louis is to become a dad after a brief fling with Los Angeles-based stylist Briana.