Hi, strange one. I have found online a dedicated site to the Halstead Family. According to that, Lawrence had the one child Oliver.
Laurence HALSTED
1485 to 1570
Relationship
5th great-grandson of William de HALLSTEDES
Research Note: At Rowley, Laurence HALSTED was born before 1480. He was the son of Oliver HALSTED.
Child of Laurence HALSTED is Oliver HALSTED+ b. b 1520, d. Nov 1582
Asking where have the other children on this profile come from? I cannot find any records for these additional children apart from other Trees which may not necessarily be correct. Can you advise at all please