Jill and Derick Dillard from "Counting On" are overjoyed since they are expecting their second child, and the Christian couple believes their 20-month-old son Israel David is going to make an amazing big brother.

"We were really excited when we found out we were expecting," Jill, 25, said in a video clip for TLC. "I had been through tons of pregnancy tests, one of those big online value pack things. I had been going through pregnancy tests, so whenever I got positive pregnancy tests — I took like three — I was like, 'Ah, really?'"

Another thing they're excited about is seeing their firstborn son embrace the role of big brother. "Israel's going to be a great big brother. He already loves other little babies," said the expectant mom. "The only thing I think he'll have to work on is just learning that babies that are smaller than you, you have to be more gentle with."

Her husband Derick, 27, added: "Israel's going to be a fantastic big brother."

The happy couple, who started their own family ministry in Central America, announced their second pregnancy a couple of days ago by posting on their blog. They shared a family photo with Israel holding up a sign that reads: "I'm being promoted to big brother." Jill, who was wearing a yellow sweater, is already showing her baby bump.

"Words cannot describe how excited we all are that God has blessed us with another precious gift!" she and her husband shared in a joint message. "We are eager for another sweet Dillard baby to join our lives come July, and we know Israel will be a great big brother. Don't forget to check back here often for updates on our family and our ministry and remember to tune in Counting On on TLC as this pregnancy unfolds! We are so excited!!!"