If you have connected any workflows to a pernr via BUS1065 (like it is described here), you can receive all related workflows/workitems related to this pernr via the following code:
NEW cl_def_im_com_bsp_workflow( )->if_ex_com_bsp_workflow~read_workitems_for_object( EXPORTING iv_swo_objtype = 'BUS1065'
iv_swo_objkey = CONV #( lv_pernr )
IMPORTING et_workitems = DATA(lt_workitems) ).
LOOP AT lt_workitems ASSIGNING FIELD-SYMBOL(<workitems>).
"If you are only interested in specific workflows, you could filter here
"WHERE wi_rh_task = 'WSxxxxxxxx'
"AND wi_stat = 'STARTED'.
NEW /iwwrk/cl_wf_read_workitem( <workitems>-wi_id )->get_wi_container( IMPORTING et_wi_container = DATA(lt_wi_container) ).
" access container items via lt_wi_container[ element = 'IV_PERNR' ]-value
ENDLOOP.