On the surface, it seemed like a happy marriage.

There were smiling photographs of the blissful couple. They appeared to be sharing a home in Corona. The bride had even picked out her groom’s wedding ring.

But federal authorities say the union was sham.

The wedding ring was a $50 bargain-bin item, purchased more than a year after the purported marriage ceremony, prosecutors allege. The photographs were staged, and the husband was growing more anxious by the day. Privately, he told friends he was worried the couple weren’t clicking. On social media, he published a desperate post admitting he was involved in terrorist plots and might go to prison for fraud, court records show.

Thursday, FBI agents arrested the wife, Mariya Chernykh, her sister, Tatiana Farook, and her brother-in-law, Syed Raheel Farook, whose younger brother was one of the two terrorists responsible for the San Bernardino shootings that killed 14 at the Inland Regional Center in December.

The arrests were the latest development in the FBI’s ever-widening investigation into the attacks carried out by Syed Rizwan Farook and his wife, Tashfeen Malik. The couple died in a gun battle with law officers hours after the killings.