Kate Middleton is unhappy about Pippa Middleton's recent engagement with James Matthews, a source told Life & Style magazine. According to the report, the reason behind tensions between the two sisters is James' younger brother Spencer Matthews.

"[Kate] is horrified about Spencer being Pippa's brother-in-law," the source told Life & Style magazine, which also reported that the Duchess of Cambridge was concerned as Spencer had appeared on several reality shows and openly admitted to experimenting with drugs.

"Spencer has slept his way around London and left a lengthy trail of angry women in his wake," another source told the magazine. "Kate's concerned. The last thing she wants is for William's family to turn against her because of Spencer's actions."

Last month, InTouch Weekly reported that the two sisters are at war with each other as Pippa is "fed up with Kate’s judgmental attitude."

"After years of private drama, clashing views about courting attention and fresh concerns about a wild brother-in-law-to-be, Pippa doesn’t want Kate in her wedding party,” a source told InTouch Weekly. “She’s fed up with Kate’s judgmental attitude, and doesn’t want her to be a bridesmaid unless she starts to chill out.”

However, this report was debunked by Gossip Cop which stated that there is no feud between Kate and Pippa.

Last week, Life & Style magazine had also reported on Kate's concern that Pippa's future brother-in-law may reveal family secrets in a bid to gain popularity.