You've no doubt heard of Dividend Aristocrats, stocks in the S&P 500 that have increased their dividends for 25 consecutive years. But the true royalty among dividend stocks are the Dividend Kings. These stocks have boosted their dividends for at least 50 years in a row.

Not all Dividend Kings are worthy of holding sway in your portfolio, though. Some are quite expensive compared to their growth prospects. Others don't have strong economic moats that protect them from competition. Several of the Dividend Kings don't even offer dividend yields that are very attractive.

But there are some Dividend Kings you can buy and hold forever. Five that especially stand out are ABM Industries (NYSE:ABM), Dover Corporation (NYSE:DOV), Johnson & Johnson (NYSE:JNJ), Lowe's (NYSE:LOW), and Parker-Hannifin (NYSE:PH).

Gold chess king and fallen silver chess king next to hundred dollar bills, all on top of a jigsaw puzzle

Image source: Getty Images.

1. ABM Industries

ABM Industries is an integrated facilities solutions company. It provides janitorial, facilities engineering, and parking services for commercial real estate properties, businesses, educational institutions, and sports and entertainment venues as well as a range of services to airports, hospitals, and non-acute facilities. 

The company has paid a dividend every year since 1965. ABM's dividend currently yields 1.97%.

Although the company's services might not be the most exciting, ABM's business model is solid. The company continues to make strategic acquisitions and divestitures that should keep it at the top of the market for facilities solutions, ensuring that those nice dividends keep flowing.

2. Dover

Dover is a diversified global company that provides specialized equipment, components, and consumables for multiple industries. It focuses primarily on selling to businesses operating in the chemical, consumer goods, digital textile printing, environmental solutions, industrial, oil and gas, retail fueling, and vehicle service markets. 

The company's streak of increasing its dividends annually goes back 64 years. Dover's dividend yield currently stands at 1.97%.

In 2018, Dover initiated a corporate restructuring that reduced costs and shifted its portfolio to focus on higher-margin businesses. That effort appears to have paid off, with shares soaring around 40% so far this year. Dover should now be in an even better position to continue rewarding shareholders with higher dividend payments for a long time to come.

3. Johnson & Johnson

Johnson & Johnson ranks as the largest healthcare company in the world. The company has over 260 businesses across the world that develop and market consumer healthcare products, medical devices, and pharmaceuticals.

J&J has increased its dividend for 57 consecutive years. Its dividend yields 2.91% -- the highest level among these top five Dividend Kings.

The company stands to benefit from aging demographic trends that should drive higher demand for healthcare products and services over the long term. J&J's breadth of operations across the healthcare continuum also enable it to offer bundling deals to customers that give the company a competitive advantage over its peers.

4. Lowe's

Lowe's is the second-largest home improvement retailer in the world, trailing behind Home Depot. These two companies enjoy a near-duopoly, competing primarily against each other and smaller home improvement stores.

Unlike Home Depot, though, Lowe's has an impressive track record of dividend hikes that began in 1961. The company's dividend currently yields 1.95%.

While Lowe's is still No. 2 in the market, it beat Home Depot in the latest quarter on the important metric of comparable-store sales growth. Although there is some volatility in the home improvement sector, Lowe's has shown that it can survive and thrive, making it likely that its dividend streak will keep going.

5. Parker-Hannifin

Parker-Hannifin is a leading global manufacturer of motion and control technologies and systems for a wide variety of mobile, industrial, and aerospace markets. It sells hundreds of thousands of products, including pumps, motors, seals, and valves, with no single product making up more than 1% of its total revenue.

The company has paid a dividend for 63 consecutive years. Its dividend yield currently stands at 1.97%.

Parker-Hannifin's fiscal 2019, which closed in June, was the company's best year in its history. Its decentralized organizational structure fosters an atmosphere of innovation that enables Parker-Hannifin to continue winning customers' business. And that means the dividend payouts should keep rising for years to come.