Both the "Katzenjammer Kids" and the "Captain and the Kids" appeared in a number of different comic books.  I'll not attempt anything near a complete treatment here, but the following will give you an idea of what they were.

There were 151 issues of Ace Comics published by David McKay Publications between April 1937 and November 1949.  Most, if not all of them, contained reprints of the Katzenjammer Kids newspaper strips, along with other reprint titles such as Krazy Kat, Jungle Jim, and Blondie.  Many of the issues featured the Katzies on the cover.

From May 1937 through 1948, David McKay Publications also published "Feature Books," a comic that rotated newspaper reprints of several different strips, including Dick Tracy, Popeye, and the Phantom.  The Katzenjammer Kids appeared in six issues between 1942 and 1946.  The last of these (#37), shown here, includes a page that features a photo and short biographical sketch of artist H.H. Knerr.

The comic book actually entitled "The Katzenjammer Kids" ran for 27 issues between 1947 and 1954.  It was published first by David McKay, then by Standard and, finally, by Harvey.  Some of these issues contained original stories, as opposed to newspaper reprints.  The special issue (#26) shown here was printed partially in "3-D" a fad of the time.  I'll wait while you go find that old pair of blue/red 3-D glasses that you have around the house somewhere.

The first comic book appearance of the Captain and the Kids seems to have been in issue #1 of "Single Series Comics," seen here.  The contents were reprints of the newspaper comic strip.  Collectors should note that that this 1938 comic was reprinted in 1939, something of a rarity for a comic book.

Beginning with issue #30 the title changed to "Comics On Parade."

Comics On Parade ran from 1942 until 1955.  The Captain and the Kids newspaper reprints appeared along with those of Nancy and Li'l Abner, the three titles alternating appearances on the cover.

Images on the covers of Comics On Parade are original, uncredited, illustrations and are among the best renditions of these characters that you will find.

Tip Top Comics, published by United Features Syndicate, ran for 225 issues from April 1936 until May 1961.  The Captain and the Kids newspaper reprints appeared along with those of Tarzan, Li'l Abner, and Fritzi Ritz, among others.

Issues of Tip Top comics that featured the Captain and the Kids were often quite exceptional.  You'd be hard pressed to find a more colorful and appealing image of these characters than this one.

Sparkler Comics, also published by United Features Syndicate, ran for 120 issues from July 1941 until January 1955.  The Captain and the Kids newspaper reprints appeared along with those of Tarzan, Abbie and Slats, and Nancy, among others.

As with the Tip Top covers, those issues of Sparkler that featured the Captain and the Kids displayed "Katzie" graphics that are among the best to found anywhere.