The 27-year-old, who is expecting their third child, marked the occasion by revealing the sex of their little one.
"My baby boy," she wrote on her Instagram Stories May 14 while holding up a sonogram, per a screenshot shared by People. "Happy Mother's Day."
The news comes less than a month after Jimmie and Lexi—who are parents to daughters Naomi, 3, and Zara, 19 months—shared the pregnancy while simultaneously announcing their split.
"After much thought and reflection in recent months, Lex & I have made the decision to separate," the country music singer wrote in an April 21 Instagram post. "As we navigate this life change, we can also share that we will be welcoming another child together later this year."
Jimmie—who is also dad to son Aadyn, 8, from a previous relationship—noted the exes' "number one priority is and always be ensuring that our children are healthy, happy and loved." He added they "remain committed to co-parenting with love and respect for one another."
Jimmie and Lexi filed for divorce in Tennessee the following week and cited irreconcilable differences as the reason for their breakup, according to documents obtained by People.
Then in early May, a former manager of the musician, identified as "Jane Doe," filed a lawsuit in which she accused him of sexual assault and harassment, according to court documents obtained by E! News. Jimmie has denied the allegations.
"It is deeply troubling and hurtful that someone I counted as one of my closest friends, colleagues and confidants would make allegations that have no truth to them whatsoever," the singer said in a statement obtained by E! News May 11. "I acknowledge that we had a sexual relationship—one that lasted for nearly two years. During that time she never once accused me of any wrongdoing, and she spoke of our relationship and friendship as being something she wanted to continue indefinitely. Only after things ended between us, did she hire a lawyer to reach out and ask for money, which leads me to question her motives."
The 37-year-old added, "The simple fact is, her accusations are not only false, but also extremely damaging. I've worked incredibly hard to build my career, and I intend to mount a vigorous defense to her claims and take all other legal action necessary to protect my reputation."
In response, Jane Doe's attorney Elizabeth Fegan said in a May 12 statement, "The only ask we made of Allen and his legal counsel was to meet to discuss Allen's behavior and resolution of our client's claims. At no time did our client make a monetary demand. The response was a hard no, and colored with threats that his team would take steps to publicly tarnish my client. My client had no choice but to be proactive in protecting herself by filing the complaint."