His mother was a daughter of Alfred Lämmerhirt, who founded the predecessor company of Westfalia Dinnendahl Gröppel in 1872.

He grew up on his father's estate located at Hauptstrasse 145 in Warstein, close to his cousins, which also lived on the property and would later engage in business activities with him in the family conglomerate.

Initially, Siepmann and his brother were employed as directors and took-over the management and technical development of the company, which at the beginning was still known as Peters & Co.

During his tenure in the management of Siepmann he also became involved in various board of directors as well as advisory board roles such as with Commerzbank, one of the major banking corporations in Germany as well as the Mechanical Engineering Industry Association (VDMA).Due to the Great Depression the company struggled and had to reduce staffing from 400 (1927) to 140 (1932), only in 1933 the company became a benefactor of the growing Nazi Germany, which needed suppliers for armament orders.

Since 1937 the Siepmann company was the second largest drop forge factory in Germany and one of the most modern in entire Europe.

In 1946, they formed the subsidiary PERSTA Steel Fixtures GmbH & Co KG and the third generation entered management of the company.

[2] In the course of his work in management, he developed numerous international patents for applications (Valves, housings and fittings).

Her maternal grandfather Heinrich Wilke gained substantial wealth through mining and merchant activities in German South West Africa and Australia.